Retractable mast



y ,1 H. N. EKBOM EIAL 2,348,285

RETRACTABLE MAST Fild May 26, 1941 2 Sheets-Sheet 1 I INVENTOR. Hum-RN-EKBOM BY LUTHER H. CROW ATTO/PIYEX May 9, 1944. N. EKBOM Er LRETRACTABLE MAST Filed May 26, 1941 2 Shegts-Sheet 2 INVENTOR. H/L/Yfl?N. 'E/(BO/Y LUTHER H. CROW Patented May 9, 1944 2,348,285 RETRACTABLEMAST BilmerN. Ekbom and Luther H. Crow. Cedar Rap ids, Iowa, assignorsto Link-Belt Speeder Corporation, Chicago, 111., a corporation ofIllinois lApplication May 26, 1941, Serial No. 395,260 3 Claims.(01.212-59) This invention relates to power driven cranes and shovelsand the like, and has particular relation to a retractable mast forsupporting the boom assembly of such devices.

In power driven devices such as lifting cranes,

is pivotally mounted on the forward end of the raise and lower the boomby means of a boom hoist cable, operating over a plurality of sheaves toprovide the required amount of lifting power, and extending between theouter end of 'the boom and a fixed anchor point in the framework of thebody of the crane, whichfanchor point is disposed as high as possibleabove the supporting frame. It is the usual practice to place this fixedanchor point for the boom hoist cable as high as possible within theoperators cab of the crane, usually near the roof line thereof. Thus itwill be seen that the angle of incidence between the hoisting cable andthe boom hoist is usually limited by the height of the crane cab, andthe smaller this angle is, the greater the strain on the boom hoistcable and the boom. Obviously the length of the boom and the load whichmay' frame of the device, it is the usual practice to be safely carriedby the outer end of the boom is determined by the load which the boom,hoist cable and the boom may safely carry.

Fixed mast structures, extending well above the cab and providing ananchor point for the cable, have been employed for. increasing thisangle of the b0 hoist cable'relative to the boom in order to permit useof longer booms and to increase the lifting ca acity of the boom. Suchfixed mast structures, ho ever, are impractical and undesirable since itis usually necessary to entirely remove or dismount such a device from acrane before the crane can pass under bridges, viaducts or the likewhen'it is being transported on the highway. This is, of course, auseless and time-consuming operation.

structure shown in Figure 3.

. It is accordingly a general object of our invention to provide animproved mast structure for supporting the booms of cranes and the like.

It is anotherobject of our invention to provide a retractable mastthrough which the boom hoisting cables may be reeved and secured, whichmast may be extended any desired distance above the cab or frame of thevehicle and which may be quickly and easily folded or retracted toreduce the over-all height of the crane structure whereby it may be morereadily transported from job to ob. I J Itis another object of ourinvention to provide a retractable mast structure which may be readilyand easily raised-or lowered by means of the boom hoisting equipment andwithout the necessity of employing either auxiliary equipment .or manualeffort to place the mast in operative position:

It is a further object of our invention to provide a retractable mast ofthis nature which may be employed in supporting and raising or loweringthe boom when the mast is in either its extended or lowered position.

Other and further features and-objects of the invention will be moreapparent to those skilled in the art upon a consideration of theaccompanying drawings and following specifications, wherein is discloseda single exemplary embodiment of the invention, .with the understanding,however, that such changes may be made therein as fall within the scopeof the appended claims, without departing from the spirit of theinventionl In said drawings:

Figure l is a general view in side elevation of a crane employing aretractable mast constructed in accordance witha preferred embodiment ofour invention.

of the retractable mast assembly and illustrating,

in particular, the method of rigging the boom hoist line. The view istaken from a plane extending parallel-to the plane of the boom hoistlines rather than ina horizontal plane above the machine.

Figure 3 is a view in side elevation of the retractable mast structureand the means employed in mounting it upon the main frame of the crane.

Figure 4 is a view in rear end elevation of the Figure 5 is afragmentary view in top of the device shown in Figure 3 andillustrating, in particular, the bail to which the boom hoist cable issecured.

Figure 6 is a fragmentary view in front elevation of the device shown inFigure 3- illustrating,

in particular, the relationship of the various members of the framework,and

Figure 'l is a fragmentary view, partly in top main framework or base llmounted for rotation on a turntable or bull ring H, which turntable ismounted upon a sub-frame and endless or elevation the drawings, and toFigure 1- spaced, rea

- weight:

, caterpillar treads l3 in accordance with the usual practice. A boom I4is pivotally mounted, as indicated at It, in-brackets l3 secured on theforward ends of the main frame members ll. Hoisting drums It for theboom-hoist cable I1 and the load hoisting cable i8 are mounted forrotation in a framework 21 which is secured to the main frame II. Thedrive and control of these hoisting drums, as well as of the tractiondrive and steering mechanism, may be provided in any convenient orconventional manner.

The boom supporting mast comprises, in general, a permanent or fixedlower mast structure indicated generally at 2|, an upper, retractablemast, indicated generally at 3| pivotally connected at the upper end ofthe lower mast structure on shaft 24, a cable ball 62 'pivotallyconnected at the upper end of the retractable mast,

' tension members indicated generally at 33 for retractable maststructure is best shown in Fisures 3 to '1, inclusive.

The lower. mast structure preferably includes a pair of rigidcompression members 22 pivotally secured at their lower ends, as at 23,to the brackets it near the forward ends of the main frame members I i.These compression members extend upwardly and rearwardly at an angle tothe boom and to a point near the roof line of the cab of the crane, theupper ends of these members being provided at that point with a pair oflaterally extending openings for the reception of a cross shaft 24. Thisshaft 24, as well as the compression members,

are held firmly in fixed position by means of" tension members 28, saidtension members being provided with openings at their upper ends forreception over the shaft 24, and openings in their lower ends to providefor pinned connection 23 to the hoisting drum framework 21. Thesetension members may of course extend downwardly the entire distance tothe main frame members Ii.

The upper or retractable mast includes a pair of'rigid compressionmembers 3i provided with openings in their lower ends for reception forpivotal movement on the shaft 24. The upper ends of these compressionmembers 3| are also provided with openings for the reception of'an upperor shaft 32 on which shaft a, pair of ardly' anddownwardly extendingtension mem ers 33 are pivotally mounted.

The anchoring structure 34, to which the ten sion members 33 may besecured, preferably comprisestwo pair of strap-members 35' and 36disposed in spaced relation and extending vertically adjacent the rearwall 31 of thecab. These anchoring members 33 and 36 are secured'bymeans of pins 33 to mounting brackets 39 which may be, in-the form offiat bars fixedly secured as by welding or riveting to the main framemembers I I and extending beyond the rearmost ends thereof. Thesemounting brackets are preferably provided with flanges 44 at their loweredges, which flanges may be bolted directly to the crane counter-weight42 so as to not only aid in supporting the coupter-weight, butto'transfer a large portion of the boom load directly to the counter-These verticalanchoring members 35 and 33 are held in fixed relation tothe fixed mast structure 2| by means of rigid spacing members 43, theforward ends of which are provided with openings for reception on theshaft 24, and the rear ends of which are provided with other openlugsfor pinned connection 44 between transversely extending angle members 43and 41, which angle members are secured, as by welding, near the upperends and to the forward edges of the anchor strap members 33 and 36. Adetail of this structure is shown in Figure 7.

The lower ends of the upper mast tension members 33 are provided withopenings which may be aligned with companion openings in the upper endsof the anchor straps 38 and 36, through which openings the pins it maybe inserted and secured by cotter keys or the like to support theretractable mast in extended or operating position. These tensionmembers 33 are connected together by transverse braces 42 and diagonalbracing members 43, which members serve to brace the entire uppermastassembly.

The upper mast may be lowered, as will hereinafter be described, uponthe removal of the pins 5i. Openings 52 are provided in the anchormembers 35 and 33 at spaced distances from the ings in the lower ends ofthe tension members 33 to secure the mast in its lowered position.

The boom hoist ca-ble l'l (Figures 1, 2 and 3), extends from one of thehoist drums i9 upwardly, over the free running sheave 83 which ismounted on the cross shaft 24, and then forwardly to a block" 51,secured by the boom cables 33 to the outer end of the boom; This boomhoist cable is reeved back and forth over a plurality of sheaves in this"block" 51 and in a companion block" 33 which is supported from theupper end of the retractable mast, and the end of the cable is broughtback and fixedly secured by a lug or strap 8| to the cross shaft 24.

The cable "block" 59, instead of being secured directly to the upper endof the retractable mast, is swingably secured to the cross shaft 32atthe upper end of the mast by means of a ball 62, the structure ofwhich is best shown in Figure 5;

This bail preferably includes 9, pair of straplike members 63 spacedapart near their midpoints by the pipe spacing member 34 and securedtogether by a rod itjthreaded on its ends to receive nuts. These members33 are provided at their rearward ends .with openings which are hushedor provided with collars as indicated at 61, for reception of and forpivotal movement on the cross shaft 32. A short length of pipe -33, alsoreceived over this shaft 32, serves to hold these rear ends of the strapmembers 33 in proper spaced relation. The ball members 63 are providedat their forward ends with companion pairs of spaced plate-like members33, the lower edges of which project downwardly to provide spacingmembers which may contact the cross shaft 24 when :the retractable boomis lowered, but which will hold the forward end of the ball a spaceddistance above the said cross shaft 24.

Theblock 53 may be constructed with a pair of spaced opposed channelmembers 13 and 11 ha ng the sheaves I3 disposed for rotation theebetween. The channel members 16 and 11 are secured as by welding to endplates 13, which end plates, have rear extensions receivable bebers the"block" may be secured b means i h pivotpinul. 1 t e place The operationand manner of using the device may be better understood from thefollowing description. Assuming that the retractable mast is in extendedposition, as illustrated in Figures 1 and 3, it will be apparent thatthe boom may be raised .or lowered as desired and may be controlled bythe boom hoist cable drum, and that a considerable increase in leverageis afforded in the lifting of the boom by the increase in the anglebetween the boom hoist cable and the boom. When, however, it isdesirable or necessary to reduce the head room required by the vehicle,as when thedevice is to be moved under a viaduct or across a bridge, theboom may be lowered to the surface of theg'round, and as the boom hoistcable becomes slack after the boom reaches the ground, the strain willbe removed from the tension members 33 and the attachment pins 5| may beremoved. The operator may then continue to slack up onthe boo'm hoistcable, which will permit the retractable mast compression members 3| tosink slowly rearwardly and downwardly, and the tension members to slideassaaas though adapted to follow the movement of the the slack in theboom hoist cable while the boom I rests on the ground and until the rearend of the retractable mastis lifted upwardly to the proper height, atwhich position it may be locked in ings in the anchor straps. 1

by n rtinK th pins II in the proper open- Although we have describedaspecific embodiment of our invention, it is apparent that modie, asupporting structure, a boom structure for swinging movementin thevertica longitudinal plane of the supporting structure, i. bailpivotally secured to the upper endof the upper mast structure andextending forwardly in the direction ofthe boom, a boom hoist cableextending between the free end of the bail and the boom hoist, rigidmeans for. supporting the upper end or the upper mast structure ineither upwardly extended position or in lowered position substantiallyparallel with the roof of the crane, and spacing means for providing alengthened lever arm between the point of attachment of the cable andbail'and the pivotal mounting point of the upper mast and preventinginterference between the boom hoist cables and the upper end of thelower mast structure whereby direct lifting effortis applied to theupper end of the upper mast before the boom is lifted from the round.

2. In a device of the character described, a

mobile supporting structure, a gantry, a shaft mounted in the upp rportion of said gantry, a retractable mast pivotally supported by saidshaft and extending rearwardiy and normally upwardly therefrom andadapted, in retracted position, to lie substantially parallel with theground, a boom pivotally mounted on the supporting structure, a. bailpivotally connected with the free end of the mast, a boom hoist cableoperatively connecting the free end of said bail and the boom, the saidbail being rigid and of a length at least substantially equal to that ofthe mast, and means for supporting the free end of said ball in spacedrelation to and above the shaft whereby a lever am, having a lengthequal to the distance provided by the supporting means between the saidshaft and the bail, is providedat an angle to and extending upwardlyfrom the mast at its pivotal mounting point and to which lever armlifting.

effort may be applied by the boom hoist cable when the boom is loweredandthe mast is in retracted position .and below the dead center thereofrelative to the said shaft.

. 3. In a structure of the class described, a base,

a mast support on the base, a mast pivotally mounted on the mastsupport, a rigid tension memberto restrain upward and forward movementof the mast, and a tension member support pin-connected to the base andhaving a plurality of spaced-apart connecting means to permit connectionof the tension m her to the tension member support in a no raised work sposition or in a loweredworking position to reduce overall height, thetension members being rigid to support the mastdn raisedor loweredposition whether'ornotthere isaload onthemast and wherebythemastwillcarryboomload'in-raised or lowered position. r

m :1. most.

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